JP2689580B2 - Motion detection circuit - Google Patents

Description

The present invention relates to a composite television signal (hereinafter referred to as "V signal") in which a color signal is frequency-multiplexed in a high frequency region of a luminance signal.
Motion adaptive YC separation device for separating a luminance signal (hereinafter referred to as “Y signal” or simply “Y”) and a chrominance signal (hereinafter referred to as “C signal” or simply “C”) from each other, or interlace The present invention relates to a motion detection circuit suitable for motion detection used in a motion adaptive scanning line interpolation device for converting a television signal for scanning into progressive scanning.

[Conventional technology]

A motion adaptive YC separation device and a motion adaptive scanning line interpolation device using a conventional motion detection circuit locally determine whether an image is a still image or a moving image, and perform YC suitable for the pixel signal of each part. Separation and scan line interpolation are performed.

Since the configurations of motion adaptive processing devices such as these devices are basically the same, the motion adaptive YC separation device will be described as an example.

In the current NTSC signal system, a composite signal is obtained by frequency-multiplexing the C signal in the high frequency range of the Y signal. Therefore, the receiver needs YC separation, and the imperfect separation causes image quality deterioration such as cross color and dot crawl.

Therefore, with the recent development of large-capacity digital memories, motion adaptation using a delay circuit having a delay time equal to or longer than the vertical scanning frequency of a television signal (hereinafter, simply referred to as "delay circuit"). Various signal processing circuits have been proposed for improving image quality such as YC separation.

FIG. 7 is a block circuit diagram showing an example of a conventional motion adaptive YC separation device. In FIG. 7, the NTSC system V signal 101 is input to the input terminal 1 and the YC in the field is input.
It is applied to the input terminals of the separation circuit 4, the inter-frame YC separation circuit 5, the Y signal motion detection circuit 6 and the C signal motion detection circuit 7, respectively.

In-field YC separated YC by an in-field filter (not shown) in the in-field YC separation circuit 4.
The separated Y signal 102 and the intra-field YC separated C signal 103 are input to the first input end of the Y signal mixing circuit 9 and the first input end of the C signal mixing circuit 10, respectively.

In addition, an inter-frame YC separated Y signal 104 that is YC separated by the inter-frame filter in the inter-frame YC separation circuit 5,
The inter-frame YC separated C signal 105 is input to the second input end of the Y signal mixing circuit 9 and the second input end of the C signal mixing circuit 10, respectively.

On the other hand, the Y signal motion amount 106 detected by the Y signal motion detection circuit 6 is input to one input end of the synthesizing circuit 8 and the C signal motion amount detected by the C signal motion detection circuit 7
107 is input to the other input terminal of the combining circuit 8.

The motion detection signal synthesized by the synthesis circuit 8 is the control signal 10
8 is inputted to the third input end of the Y signal mixing circuit 9 and the third input end of the C signal mixing circuit 10, respectively, and the Y signal motion detecting circuit 6, the C signal motion detecting circuit 7 and the synthesizing circuit 8 detect the motion. It constitutes the circuit 70.

Motion-adapted YC-separated Y signal output from Y signal mixing circuit 9
109 is sent from the output terminal 2.

Further, the motion adaptive YC separated C signal 110 which is the output of the C signal mixing circuit 10 is sent from the output terminal 3.

Next, the operation of this conventional example will be described. The motion detection circuit 70 combines the outputs of the Y signal motion detection circuit 6 and the C signal motion detection circuit 7 in the YC separation of the V signal 101 by the combining circuit 8 to represent an image in which the V signal 101 is stationary. It is discriminated whether it is a signal or a signal representing a motion.

As shown in FIG. 8, the Y signal motion detection circuit 6 inputs the V signal 101 from the input end 31 using the 1 frame delay circuit 33 and the subtractor 34 to obtain the 1 frame difference of the Y signal, After passing through a band-pass filter (hereinafter referred to as “LPF”) 35, an absolute value circuit 36 obtains an absolute value, and the non-linear conversion circuit 37 converts the absolute value into a signal 106 indicating the amount of movement of the low frequency component of the Y signal. And outputs it to the output terminal 32.

Further, the C signal motion detection circuit 7 inputs the V signal 101 from the input end 11 and uses the two-frame delay circuit 15 and the subtractor 16 to calculate the two-frame difference, as shown in FIG. After passing through a pass filter (hereinafter referred to as “BPF”) 25, the absolute value circuit 18 obtains the absolute value, and the non-linear conversion circuit 19 obtains the absolute value of the signal 10 indicating the amount of movement of the C signal.
It is converted to 7 and output to the output terminal 12.

The synthesizing circuit 8 is configured to select and output the larger value of the Y signal motion amount 106 and the C signal motion amount 107, for example.

This determination result is expressed in the form of a motion coefficient k (0 ≦ k ≦ 1). For example, when it is determined that the image is a still image, k = 0, or when the image is determined to be a completely moving image. , The Y signal mixing circuit 9 such that k = 1.
The control signal is given to the C signal mixing circuit 10 as 108.

In general, when an image is a still image, YC separation between frames using inter-frame correlation is performed, and a Y signal and a C signal are separated.
Separate signals.

The inter-frame YC separation circuit 5 uses, for example, a 1-frame delay circuit 44 and an adder 45 as shown in FIG.
The V signal 101 is input from 41, the one frame sum is calculated to extract the YF signal 104, and the YF signal 104 is output from the output terminal 42 and the YF signal 104 is subtracted from the input by the subtractor 46.
05 is extracted and output to the output terminal 43.

Further, in general, when the image is a moving image, the Y signal and the C signal are separated by performing the intra-field YC separation using the intra-field correlation. The in-field YC separation circuit 4 inputs the V signal 101 from the input terminal 51 as shown in FIG. 11, and uses the 1-line delay circuit 54 and the adder 55 to obtain the 1-line sum and extract the Yf signal 102. Then, the Yf signal 102 is subtracted from the input by the subtractor 56 while being output to the output end 52, and the Cf signal 103 is extracted and output to the output end 53.

In a motion adaptive YC separation device, such YC
The separation circuit 4 and the inter-frame YC separation circuit 5 are juxtaposed, and the motion signal k synthesized by the synthesis circuit 8 causes the Y signal mixing circuit 9 to perform the following calculation to perform the motion adaptive YC separation Y.
The signal 109 is output.

 Y = kYf + (1-k) YF Here, Yf: YC separation Y signal output in the field 102 YF: YC separation Y signal output 104 between frames.

Similarly, the control signal 108 causes the C signal mixing circuit 10 to perform the following operation, and the motion adaptive YC separated C signal 110
Is output.

 C = kCf + (1-k) CF Here, Cf is the intra-field YC separated C signal output 103 CF is the inter-frame YC separated C signal output 105.

The motion adaptive Y signal 109 and the motion adaptive C signal 110 are sent from the output terminal 2 and the output terminal 3, respectively.

In this motion adaptive YC separation device, the C signal motion detection circuit 7 can also be realized by the configuration shown in FIG.

In FIG. 12, the V signal 101 is input from the input terminal 11, and the color demodulation circuit 13 outputs two types of color difference signals RY and B-.
It is demodulated to Y. These two types of color difference signals are time-division multiplexed at the frequency of the time-division multiplexing circuit 14, and a 2-frame delay circuit 15 and a subtraction circuit 16 obtain a 2-frame difference. The Y signal component is removed from the two-frame difference through the LPF 17, the absolute value is obtained by the absolute value circuit 18, and the nonlinear conversion circuit 19 performs nonlinear conversion to output the color signal motion detection amount 107 from the output end 12.

[Problems to be solved by the invention]

Since the conventional motion adaptive YC separation device is configured as described above, the motion detection circuit 70 converts the motion amounts detected by the Y signal motion detection circuit 6 and the C signal motion detection circuit 7 into the combined amount. Based on this, the Yf signal 102 and the Cf signal 103 by the intra-field YC separation, and the YF signal 104 and the CF signal 105 by the inter-frame YC separation are respectively mixed.

For example, in the C signal motion detection circuit 7, if motion detection is performed by taking the difference in color units of the color difference signals color-demodulated as shown in FIG. 12, color demodulation is performed as shown in FIG. Two types of color difference signals, FIG. 13 (a) and FIG.
When FIG. 13B is time-division-multiplexed to be as shown in FIG. 13C, assuming that there is no change in the Y signal, the difference in frame units is as shown in FIG. 13D. Become.

As an example, consider a pattern with a different hue and a fixed color amplitude of 1. At this time, for example, when a red object (hue 90 °) moves, the difference in frame units does not have a BY component as shown in FIG. 13 (e), but there is a change in the RY component. However, there is a significant difference, and the amount of movement is 1 (R ₀ −R ₂
= 1).

Also, when an object having a hue of 45 ° and a color amplitude of 1 moves, the difference in frame units is 1 as shown in FIG. 13 (f).
However, the amount of movement is There is a problem that different amounts of motion are detected for different colors even for images that move in this way.

The present invention has been made in order to solve the above problems, and the motion detection amount is the same even for moving images of arbitrary colors. By detecting the optimum motion amount, cross color, dot crawl, or 2 An object of the present invention is to obtain a motion detection circuit capable of reproducing an image such as a double image with little deterioration in image quality.

[Means for solving the problem]

A motion detection circuit according to the present invention comprises means for detecting a motion amount based on a frame-by-frame difference, means for detecting a hue of a pixel of interest, and motion detection means based on the frame-based difference based on the hue detected by this means. And means for controlling the detection sensitivity of.

(Operation)

In the present invention, the amount of motion is detected according to the difference of the input signal in units of frames, and the hue of the pixel of interest is detected from the absolute values of the two types of color difference signals RY and BY,
The sensitivity of motion detection is changed according to the detected hue.

〔Example〕

An embodiment of the motion detecting circuit of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment thereof, and like FIG. 9 and FIG. 12, is a block diagram showing a detailed configuration corresponding to the motion detection circuit 7 for the C signal in FIG.

In FIG. 1, the same parts as those in FIGS. 9 and 12 are designated by the same reference numerals. The description from the time division multiplexing circuit 14 to the absolute value circuit 18 is omitted because it is the same as in FIG.

The output of the absolute value circuit 18 is input to the first input terminal of the nonlinear conversion circuit 19.

On the other hand, the V signal 101 input from the input terminal 11 is color-demodulated by the color demodulation circuit 13 into two types of color-difference signals R-Y and B-Y. It is input to the first input terminal and the absolute value circuit 20.

Also, BY is input to the second input terminal of the time division multiplexing circuit 14 and the absolute value circuit 21.

The output of the absolute value circuit 20 is multiplied by 1.14 by the coefficient unit 22 and the subtraction circuit
24 and the adder circuit 26 are respectively input to the first input terminals.

The output of the absolute value circuit 21 is multiplied by 2.03 in the coefficient unit 23 and input to the second input terminals of the subtraction circuit 24 and the addition circuit 26, respectively.

Further, the output of the subtraction circuit 24 is converted into an absolute value by the absolute value circuit 25 and input to the first input terminal of the divider 27.

The output of the adder circuit 26 is input to the second input terminal of the divider 27. The output of the divider 27 is input to the second input terminal of the non-linear conversion circuit 19 with the gain changed by the coefficient unit 28.

The output of the non-linear conversion circuit 19 is sent from the output end 12 as the motion detection amount 107 of the color signal.

Next, the operation of the color signal motion detection circuit configured as described above will be described.

Generally, an NTSC color television signal N is represented by a luminance signal Y, two color difference signals RY, BY, a color subcarrier frequency fsc, and a time t. Becomes The hue θ at this time is It is represented by

As shown in FIG. 2, when considering a coordinate system in which the horizontal axis is | B−Y | and the vertical axis is | R−Y |, the color signal that is the hue at the angle θ ^a from the | B−Y | axis has If the color difference signal is | R ^a −Y ^a |, | B ^a −Y ^a | Becomes

Now consider an axis with a 45 ° tilt from the | B−Y | axis. If the hue from this axis is ψ, the relation of ψ ^a = 45 ° -θ ^a holds, It is represented by Since the above formula is generally established, θ ^a = 45 °, ψ ^a = 0 °, tan ψ ^a = 0 θ ^a = 0,90 °, ψ ^a = ± 45 °, tan ψ ^a = 1 and RY and B The hue can be detected from -Y.

If the motion detection amount of the color signal is normalized by the size of the hue, the motion of the object having the same color amplitude is detected as the same motion amount even if the hue changes.

In FIG. 1, the absolute value circuit 20 obtains the absolute value of RY among the color demodulated color difference signals.
Multiplied by 14.

In the absolute value circuit 21, the absolute value of BY is obtained,
It is multiplied by 2.03 in the coefficient unit 23.

When the absolute value of these two types of color difference signals is subtracted by the subtraction circuit 24 and the absolute value is taken by the absolute value circuit 25, the result m is as follows.

Further, the result n obtained by adding the absolute values of the two types of color difference signals by the adding circuit 26 is given by the following equation.

The divider 27 is a circuit that divides the first input m (output of the absolute value circuit 25) by the second input n (output of the adder circuit 26), and as a result l And becomes as shown in FIG.

In FIG. 2, the horizontal axis is the absolute value of (BY) 2.03, and the vertical axis is the absolute value of (RY) 1.14.

The absolute value l of the division result is l = 0 on the straight line of 45 ° from the horizontal axis.
Then, when the angle is changed, the angle becomes larger regardless of whether it approaches the vertical axis or the horizontal axis, and l = 1 on the vertical axis and the horizontal axis.

The coefficient unit 28 in FIG. 1 can be set to a low gain as in the input / output characteristic e shown in FIG. 4 when it is desired to increase the control for the hue motion detection amount, and when the control is desired to be decreased. Is the input / output characteristic f shown in FIG.
The gain may be set high as shown in.

Further, the input / output characteristic of the non-linear conversion circuit 19 is configured as a variable characteristic as shown in FIG. 3, for example. That is, the characteristic a shows the characteristic when the difference between the absolute values of the two types of color difference signals is the minimum, and the output level of the motion detection amount is kept until the input level from the absolute value circuit 18 becomes the value A. The characteristic is that the output level gradually increases as it becomes 0 and becomes larger than A, and finally saturates. As the level of the output m of the coefficient unit 28 increases, the output starts like the characteristics b, c and d. Adjustment is made so that the point A shifts to the right and the hue does not affect the amount of motion detection.

The input / output characteristic of the coefficient unit 28 is kept constant, and the input / output characteristic of the non-linear conversion circuit 19 is changed to the input output characteristic g or h in FIG. 5 to change the characteristic of the coefficient unit 28. You can get the same effect as.

The output characteristics g and h shown in FIG. 5 do not necessarily have to change all of the rising points B and C, the slope, and the saturation level as in this example, and either one of them, or It goes without saying that a combination in which the two are changed may be used.

Further, a buffer circuit as shown in FIG. 6 may be inserted after the non-linear conversion circuit 19 so that the input / output characteristics of the non-linear conversion circuit 19 do not change suddenly depending on the pixel position.

In FIG. 6, the C signal motion detection signal 107 input from the input terminal 61 is converted into a smooth signal through a smoothing circuit 63 composed of, for example, an LPF.

If necessary, the output of the smoothing circuit 63 is reduced by the clip circuit 64 for reducing the number of bits, and the output terminal
The input from 62 is input to the synthesizing circuit 8, and malfunctions due to noise or the like can be reduced.

〔The invention's effect〕

As described above, according to the present invention, the hue of the pixel of interest is detected from the absolute values of the two types of color difference signals RY and BY,
Since it is configured to change the sensitivity of motion detection depending on the hue, it is possible to detect the motion of an object of any hue in the same way, and motion-adaptive YC with little deterioration in image quality such as cross color, dot interference, and double images. There is an effect that a motion detection circuit that enables motion adaptive processing such as separation and motion adaptive scanning line interpolation can be configured.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motion detection circuit according to an embodiment of the present invention, FIG. 2 is an output characteristic diagram of a divider in the same embodiment, FIG. 3 is a characteristic diagram of a non-linear conversion circuit in the same embodiment, and FIG. FIG. 5 is an input / output characteristic diagram of the coefficient unit 28 in the same embodiment, FIG. 5 is a characteristic diagram of the non-linear conversion circuit in the same embodiment, and FIG. 6 is a non-linear conversion circuit in another embodiment of the motion detection circuit of the present invention. 7 is a block diagram of a conventional motion adaptive YC separation device, FIG. 8 is a block diagram of a conventional YC signal motion detection circuit, and FIG. 9 is a conventional C signal. FIG. 10 is a block diagram of the motion detection circuit, FIG. 10 is a block diagram showing the detailed structure of the inter-frame YC separation circuit in the conventional motion adaptive YC separation device of FIG. 7, and FIG. 11 is the conventional motion adaptive YC of FIG. Details of in-field YC separation circuit in separation device Block diagram showing the configuration, FIG. 12 is a block diagram showing the detailed structure of the color signal motion detection circuit in a conventional motion adaptive YC separation device of Figure 7,
FIG. 13 is a time chart for explaining the operation of the color signal motion detection circuit of FIG. 4 ... In-field YC separation circuit, 5 ... Inter-frame YC separation circuit, 6 ... Y signal motion detection circuit, 7 ... C signal motion detection circuit, 8 ... Synthesis circuit, 9 ... Y signal mixing circuit, Ten
...... C signal mixing circuit, 12 …… C signal movement amount output terminal, 13 ・ ・ ・
… Color demodulation circuit, 14 …… Time division multiplexing circuit, 15 …… 2 frame delay circuit, 18,20,21,25 …… Absolute value circuit, 19 …… Nonlinear conversion circuit, 22,23,28 …… Coefficient unit , 27 …… divider, 70…
… Motion detection circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A circuit for extracting a motion amount of a color signal from two types of color difference signals after color demodulating a composite television signal in which a color signal is frequency-multiplexed in a high frequency region of a luminance signal, and a frame of an input signal. A circuit for detecting an interframe correlation for obtaining a correlation by detecting a motion amount based on a unit difference, a means for detecting a hue of a pixel of interest in a field, and the interframe correlation detection based on the hue detected by this means Means for controlling the correlation detection sensitivity of the means.